New System Installed But Somewhat Disappointed?

[KeeWay]

So I am new to solar and need some advice about the system and orientation, if this is the wrong section or type of post i apologize.

So I did the initial research for the hardware and opted for the Solar World 265 black mono panels and SMA TL inverter and working with a local company they recommended a 9.54kW system (it is supposed to eliminate my bill) and below is what they installed:

West Roof:
24 - 265W panels (2 strings of 12)
SMA SB5000TL-US-22 Inverter

East Roof:
12 - 265W Panels (1 string)
SMA SB3000TL-US-22 Inverter

I originally questioned the inverters total output because they would never be capable to hit the 9.54kW that the panels are rated at but i was assured that these can work over their rating and i would be fine. so i signed the deal and the system was installed and i was excited about the whole project and the new solar.

now i am 3+ months in the peak time and the system is not producing anywhere close to the 9.54kW the system is rated at so i started doing research about why and the first thing i found was i needed to clean the panels. so i have cleaned the panels and have even went a step further and coated the panels with a nano coating to ease the cleaning process later.

next i found on many sites the information about panel tilts and here is where i found the most interesting information in that i believe my panels are not mounted to get the most optimum outputs. so i am at 34 degrees lat in So Calif and in looking at the tilt angles it is recommended that my panels be tilted at an angle below my lat degrees to something like 29 degrees in a south facing orientation. well in learning all that my panels are mounted facing west @ 6 degrees and east @ 6 degrees matching my flat roof pitch on each side. so from the research i have done so far these do not seem to be mounted in a preferred setup. I called my installer and they pretty much said that it is too late to do anything about it so i am stuck with this setup.

am i wrong in thinking this tilt/setup is not right?

i know there are many aspects to why i would not get the full output but i just don't want to blindly sit back and accept without knowing some of the reasons. so any advice would be appreciated.


thanks
James

[silversaver]

My roof is facing SW 245 deg with about 23 deg tilt, it is not the best South facing and it is not installer's falut. It is basically how the format of my roof.

You mention you have almost flat roof of your house with 6 deg tilt?? Why not take a picture of your house using google map Sat image.

Don't you think it will be really odd if you make a 29 deg tilt south facing arrays on both of your East and West facing roof???

About the perforamce... your solar array rate 9.54kW nameplate doesn't mean you will get max of 9.54kW especially on East and West facing arrays. You need to do more reading.

[KeeWay]

My roof is facing SW 245 deg with about 23 deg tilt, it is not the best South facing and it is not installer's falut. It is basically how the format of my roof.

You mention you have almost flat roof of your house with 6 deg tilt?? Why not take a picture of your house using google map Sat image.

Don't you think it will be really odd if you make a 29 deg tilt south facing arrays on both of your East and West facing roof???

About the perforamce... your solar array rate 9.54kW nameplate doesn't mean you will get max of 9.54kW especially on East and West facing arrays. You need to do more reading.

silversaver thanks for the info, attached is a google pic of my house with the panel layouts. you can even see the tree in my front yard that i had cut down by the request of the installers because they said it would guarantee us the most outputs.
google pic.jpg

not sure it it would be odd but i see many in my area where they mounted panels on a north facing slope with racking lifting the panels up and over the actual peak to get them facing south.

i know that there are many aspects to why i cannot get the full output especially in my east/west mounting but I just want to know if the setup is wrong because everywhere i read the panels should always be facing southerly roof permitting of course but since i have a low pitch flat roof it does not seem like mounting would be a major challenge. it is just a shame that the max peak i have ever generated was ~7kWh and 55kW on the best day.

thanks
James

[silversaver]

Lots people don't like to see the solar panels from front of the house, so is my neighbor and I. You could have build stands to support South facing, but I'm not sure if you will like the look from the street view. The cost might be a little higher. It is a shame that you just found out this after the installation which nothing you can really do about it unless you spend the additional money to remove and re-install.....

[sdold]

it is just a shame that the max peak i have ever generated was ~7kWh and 55kW on the best day.

That doesn't seem that bad to me. I have 4000 watts worth of panels pointing 225 degrees (SW) on a 23 degree pitch, and the most power I typically see on a good day is around 3300 watts, generating around 23 KWh for the whole day. Proportionally, our systems are similar (your panel wattage/best day KWh ratio is almost exactly the same as mine). I assume the panel wattages are like advertised car mileage, arrived at under test conditions and good for comparison but not representing guaranteed output.

[J.P.M.]

So I am new to solar and need some advice about the system and orientation, if this is the wrong section or type of post i apologize.

So I did the initial research for the hardware and opted for the Solar World 265 black mono panels and SMA TL inverter and working with a local company they recommended a 9.54kW system (it is supposed to eliminate my bill) and below is what they installed:

West Roof:
24 - 265W panels (2 strings of 12)
SMA SB5000TL-US-22 Inverter

East Roof:
12 - 265W Panels (1 string)
SMA SB3000TL-US-22 Inverter

I originally questioned the inverters total output because they would never be capable to hit the 9.54kW that the panels are rated at but i was assured that these can work over their rating and i would be fine. so i signed the deal and the system was installed and i was excited about the whole project and the new solar.

now i am 3+ months in the peak time and the system is not producing anywhere close to the 9.54kW the system is rated at so i started doing research about why and the first thing i found was i needed to clean the panels. so i have cleaned the panels and have even went a step further and coated the panels with a nano coating to ease the cleaning process later.

next i found on many sites the information about panel tilts and here is where i found the most interesting information in that i believe my panels are not mounted to get the most optimum outputs. so i am at 34 degrees lat in So Calif and in looking at the tilt angles it is recommended that my panels be tilted at an angle below my lat degrees to something like 29 degrees in a south facing orientation. well in learning all that my panels are mounted facing west @ 6 degrees and east @ 6 degrees matching my flat roof pitch on each side. so from the research i have done so far these do not seem to be mounted in a preferred setup. I called my installer and they pretty much said that it is too late to do anything about it so i am stuck with this setup.

am i wrong in thinking this tilt/setup is not right?

i know there are many aspects to why i would not get the full output but i just don't want to blindly sit back and accept without knowing some of the reasons. so any advice would be appreciated.


thanks
James

1.) It is unlikely that any solar electric system will produce an output that equals or exceeds its nameplate (S.T.C.) rating more than for a few short periods per year, if ever. The nameplate rating and expected output will rarely if ever be equal. The instantaneous system output (Watts) will always be numerically different than the array's "size", and almost always less. That instantaneous output will vary from zero to some maximum of perhaps 80 to 90+% of the array size, depending on a lot of variables, including array orientation.

2.) This is because the input (solar radiation, or irradiance as it's called) is a continuously varying resource.

3.) The orientation (the elevation(tilt), and the azimuth (direction) of the array will have an influence on the array's total annual output as well as it's instantaneous output at any point in time.

4.) The system's greatest output will likely be when the solar irradiance is coming from a direction perpendicular to the array(s) and the most intense solar irradiance is usually around solar noon.

5.) Commonly, the greatest annual output from an array is achieved when that array faces mostly south, and an tilt angle something close to the array location's latitude. variations of 20 or so degrees in either tilt or azimuth will not affect annual output TOO much. 90 deg. (east or west) will be noticeable.

I do not want to be a butt hole about this, and you have my sympathy,but this is the type of information that is important to be aware of before purchase. It sounds as if you sort of put the cart before the horse.

However, all is probably not lost. You may not have south roof available and the arrays, while not optimal, will still produce substantial output.

Advice ?

Do this: Get familiar with PVWatts, run it for both your arrays and also a 3d way with one array consisting of the same total of panels facing south at 30 degree tilt. The difference is what you're missing.

I'd rip the vendor a new one, but their job is to sell product, not educate consumers.

Also, buy a solar for dummies book ( no offense intended, that's the name, or close to it).

[KeeWay]

1.) It is unlikely that any solar electric system will produce an output that equals or exceeds its nameplate (S.T.C.) rating more than for a few short periods per year, if ever. The nameplate rating and expected output will rarely if ever be equal. The instantaneous system output (Watts) will always be numerically different than the array's "size", and almost always less. That instantaneous output will vary from zero to some maximum of perhaps 80 to 90+% of the array size, depending on a lot of variables, including array orientation.

2.) This is because the input (solar radiation, or irradiance as it's called) is a continuously varying resource.

3.) The orientation (the elevation(tilt), and the azimuth (direction) of the array will have an influence on the array's total annual output as well as it's instantaneous output at any point in time.

4.) The system's greatest output will likely be when the solar irradiance is coming from a direction perpendicular to the array(s) and the most intense solar irradiance is usually around solar noon.

5.) Commonly, the greatest annual output from an array is achieved when that array faces mostly south, and an tilt angle something close to the array location's latitude. variations of 20 or so degrees in either tilt or azimuth will not affect annual output TOO much. 90 deg. (east or west) will be noticeable.

I do not want to be a butt hole about this, and you have my sympathy,but this is the type of information that is important to be aware of before purchase. It sounds as if you sort of put the cart before the horse.

However, all is probably not lost. You may not have south roof available and the arrays, while not optimal, will still produce substantial output.

Advice ?

Do this: Get familiar with PVWatts, run it for both your arrays and also a 3d way with one array consisting of the same total of panels facing south at 30 degree tilt. The difference is what you're missing.

I'd rip the vendor a new one, but their job is to sell product, not educate consumers.

Also, buy a solar for dummies book ( no offense intended, that's the name, or close to it).

J.P.M. thanks for the detailed info i appreciate you taking the time to post the data.

I know it is after the fact but i was just hoping that they knew what they were doing to get the most output which i assumed they were because they had me cut down the tree in my front yard. so from what you are saying it is probably not as bad as i was thinking.

i did try the pvwatts site and based on what i currently have (the largest array) if i were to go with a southerly mounting at 29 degrees at 180 degrees azimuth (compared to current of 6 degrees at 270 degrees azimuth) i would gain about 10K per year (leaving the DC-to-AC default) .


i will check out that book as well

again appreciate your advice i am just trying to make sure i got my $$ worth and grasp a understanding of it all...

Thanks
James

[silversaver]

OK. I did a calculation for you base on location Austin, TX.

With all 36 X solarworld 265W facing South with 29 deg tilt, your estimated output base on SAM result is 14,421 kWh

Now base on your current setting:

24 X solarword 265W facing West 270 deg with 6 deg tile @ 8,760 kWh

12 X solarworld 265W facing East 90 deg with 6 deg tilt @ 4,313 kWh

Total estimated annual output is 13,073 kWh


You might lost about 1400 kWh per year, but it is not really that bad after all.

Now, sit back and relax. Becasue your roof is only 6 deg tilt, so the lost isn't that much after all.

[KeeWay]

OK. I did a calculation for you base on location Austin, TX.

With all 36 X solarworld 265W facing South with 29 deg tilt, your estimated output base on SAM result is 14,421 kWh

Now base on your current setting:

24 X solarword 265W facing West 270 deg with 6 deg tile @ 8,760 kWh

12 X solarworld 265W facing East 90 deg with 6 deg tilt @ 4,313 kWh

Total estimated annual output is 13,073 kWh


You might lost about 1400 kWh per year, but it is not really that bad after all.

Now, sit back and relax. Becasue your roof is only 6 deg tilt, so the lost isn't that much after all.

silversaver i guess that does not seem as bad as i was thinking.

i feel better about the setup now but still a little mad at the installers because from what i can see the tree would have not caused any issues but it was told to us that it did make a big difference and we would loose 20% if we left it up.. oh well i guess i can just plant a new one...


thanks
James

[J.P.M.]

J.P.M. thanks for the detailed info i appreciate you taking the time to post the data.

I know it is after the fact but i was just hoping that they knew what they were doing to get the most output which i assumed they were because they had me cut down the tree in my front yard. so from what you are saying it is probably not as bad as i was thinking.

i did try the pvwatts site and based on what i currently have (the largest array) if i were to go with a southerly mounting at 29 degrees at 180 degrees azimuth (compared to current of 6 degrees at 270 degrees azimuth) i would gain about 10K per year (leaving the DC-to-AC default) .


i will check out that book as well

again appreciate your advice i am just trying to make sure i got my $$ worth and grasp a understanding of it all...

Thanks
James

You're quite welcome.

P.S.: If you use PVWatts, I'd suggest changing the derate factor from the default of .77 to something like .82 to .86 or so.

After you get more up to speed, and if you are still curious, try something called SAM from NREL. I see silver came up w/ some #'s from that source. They may well give a higer and perhaps more detailed estimate of long term performance than PVWatts. FWIW, I didn't run SAM on this one but Silver's #'s feel about right, or at least possible.

Q: Are you in So. CA or Austin ? Did I miss something ?

Good Luck.

[KeeWay]

You're quite welcome.

P.S.: If you use PVWatts, I'd suggest changing the derate factor from the default of .77 to something like .82 to .86 or so.

After you get more up to speed, and if you are still curious, try something called SAM from NREL. I see silver came up w/ some #'s from that source. They may well give a higer and perhaps more detailed estimate of long term performance than PVWatts. FWIW, I didn't run SAM on this one but Silver's #'s feel about right, or at least possible.

Q: Are you in So. CA or Austin ? Did I miss something ?

Good Luck.

J.P.M. thanks i will check them out.

yes i am in So. CAL but i ran the numbers and it was close enough to see that the system is not that bad off. i guess i will give it a year then maybe start tweaking it when i learn more and get through a winter to see what the system really produces real world.


Thanks
James

[silversaver]

Socal.... somehow I thought you were in TX..... mix with other thread

[mapmaker]

Welcome to the forum,

Here's some vocabulary to learn... "STC" and "NOCT" and "virtual tracking"

Those wattage numbers on the name plate of your panels are STC (standard temperature and conditions) numbers. As has been mentioned, in the real world your panels don't put out their STC watts... they put out NOCT (normal operating cell temperature) watts. Both STC and NOCT are standardized tests.

When you design a system you must use the STC numbers to size your wires, fuses, inverters, etc. This is because you may from time to time reach or even exceed the STC numbers.

When you design a system you must use the NOCT numbers to calculate the power produced.

Now for "virtual tracking"

Back when solar panels were very expensive, in an attempt to wring out every last watthour out of an array, trackers were invented. They are expensive, variably complex, mechanical devices that aim the array at the sun.

There's another way to increase the output of your array... just buy a few more panels. Now that panels are so cheap, it is usually (but not always) more cost effective (than adding mechanical tracker) to just buy some more panels. If you aim some of them east, and some west, you have built a virtual tracker.

A virtual tracker is not as efficient a use of your panels as a mechanical tracker, but it accomplishes the same thing for less money and more reliability.

--mapmaker

[russ]

A virtual tracker is not as efficient a use of your panels as a mechanical tracker, but it accomplishes the same thing for less money and more reliability.

The reliability of your 'virtual tracker' is 100%! Hard to beat that!

[J.P.M.]

A virtual tracker is not as efficient a use of your panels as a mechanical tracker, but it accomplishes the same thing for less money and more reliability.

--mapmaker[/QUOTE]

For most locations, I don't understand how off south panels can be as efficient as south facing panels. If you're going to add panels to make up the diff., I'd think adding them in the most advantageous orientation to the greatest extent possible would be better. What am I missing ?